The prime minister's comments were picked up on camera by ITV news, during a conversation with the monarch, the Archbishop of Canterbury and Commons speaker John Bercow, which took place at an event to mark the Queen's 90th birthday.

Speaking ahead of the government's international anti-corruption summit due to take place on 12 May, Cameron said: "We had a very successful cabinet meeting this morning. We talked about our anti-corruption summit. We've got...some leaders of some fantastically corrupt countries coming to Britain.

"Nigeria and Afghanistan are possibly two of the most corrupt countries in the world."